Superfine carbon fiber thread obtained by subjecting opene carbon fiber thread from carbon fiber raw thread to twisting, method for manufacturing the same, and strand or woven yar with the same

ABSTRACT

The purpose of the instant invention is to provide a superfine carbon fiber thread with excellent bending strength and repeated bending. To achieve this purpose, (1) a desired composite thread is produced by opening open carbon fibers, slitting the opened fibers, twisting the slit fibers and forming a composite with a composite thread; and (2) a composite thread is produced by performing a lamination process with a film (film of composite materials) while performing a fiber-opening process, and then slitting, twisting and heating the tread for stress relief.

CROSS-REFERENCE TO RELATED APPLICATIONS

The instant application is a Continuation-in-Part Application of a PCT application (PCT/JP2021/023621) designating the United States.

BACKGROUND OF THE INVENTION Field of the Invention

The instant invention relates to a superfine carbon fiber thread obtained by subjecting an open carbon fiber thread from a carbon fiber raw thread to twisting, a method for manufacturing the same, and a strand or woven yarn with the same. More particularly, the instant invention relates to a superfine carbon fiber thread obtained by subjecting an open carbon fiber thread from a carbon fiber raw thread to twisting and a method for manufacturing the same, in particular, it relates to a superfine thread obtained by forming a composite of open carbon fibers by covering and a method for manufacturing the same, as well as a superfine thread made by laminating various types of ultra-thin films onto open carbon fibers and then finishing them by a slitting machine and a method for manufacturing the same.

DESCRIPTION OF RELATED ART INCLUDING INFORMATION DISCLOSED UNDER 37 CFR 1.97 AND 1.98 (Technical Background, Part 1)

Among carbon fibers, there are mainly pitch-based carbon fibers and acrylic-based carbon fibers. Of these, acrylic-based carbon fibers are fired at 1,250° C. and depending on the aggregation state of its filaments, there are 1K, 3K, 6K, 12K, and 24K (1K refers to an aggregation of 1,000 filaments of 6 μm to 7 μm) carbon fibers. The values based on the tensile strengths of carbon fiber raw threads are calculated according to the difference in firing temperatures and published by carbon fiber manufacturers, respectively. The strength values of these raw threads were not significantly different between the carbon fibers of each manufacturer.

(Technical Background, Part 2)

Each carbon fiber manufacturer, such as Toray, Teijin, and Mitsubishi Materials, manufactures threads with acrylonitrile fibers which are carbonized at 950° C. to 3,000° C. Such threads are called raw threads, and the thickness of the filaments is 6 μm to 7 μm, and the thread made up of 1,000 filaments is called 1K and referred to as a bundle, and in addition, a bundle of 24K or less is referred to as a regular bundle (tow), and a bundle of more than 24K is classified as a large bundle (tow).

In addition, the tensile strength of the cross-section area of φ1.0 mm as a reference (φ1.0 mm/kg) is 60 kg for apparel nylon, 150 kg for industrial nylon, 320 kg for aramid kevlar, 440 kg for high strength polyethylene and 700 kg for carbon fiber.

With regard to the thread obtained by subjecting the superfine carbon fiber thread to twisting, more specifically, by giving twists numerical value times, the carbon fiber raw thread has the characteristics of being light and strong, with a specific gravity of 1.8 times, that is ¼ of the specific gravity of iron, which is 7.8, and is lighter than aluminum, which is 2.7, or glass fiber, which is 2.5. Moreover, it has excellent strength and elasticity, and the specific strength obtained by dividing the tensile strength by the specific gravity is 10 times superior than that of iron, and the specific elasticity obtained by dividing the tensile elasticity by the specific gravity is about 7 times superior than that of iron.

The tensile strength of this carbon fiber can be increased by further raising the carbonization temperature. However, standard specification carbon fiber bundles are currently fired at around 1,250° C. The representative carbon fiber bundle is TORAYCA T700 made by Toray Industries, Inc.

The inventors of the instant invention proposed a carbon fiber resin tape in Japanese Patent No. 6041416, characterized in that the carbon fiber resin tape where several carbon fiber bundles are flattened is equipped with a dry adhesive including alumina sol and potassium persulfate on the surface of the carbon fiber and in the gap of the carbon fiber. Because this has a dry adhesive, alumina sol, and potassium persulfate on the surface and in the gap of the carbon fiber, when it is used with an adhesive, it has the effect of increasing the adhesive strength of the carbon fiber resin tape.

The inventors of the instant invention proposed a twisted thread in Japanese Patent No. 6334073, comprising carbon fibers of multiple twisted threads obtained by twisting carbon fiber resin slit from a carbon fiber resin tape, with an adhesive, alumina sol, and potassium persulfate or benzoyl present between the carbon fibers of the flat fiber bundles made by flattening and expanding the carbon fibers. This invention has the effect of obtaining a twisted thread that is lightweight and has a four times greater tensile strength than stainless steel.

One of the automobile electrical components, “wire harness,” has a disadvantage that fine aramid threads that form a “wire harness” are very susceptible to ultraviolet rays, which limits its application locations. For this reason, there is a need to adapt superfine open carbon fiber threads as a new material for a “wire harness.”

BRIEF SUMMARY OF THE INVENTION

The purpose of the instant invention is to provide a superfine carbon fiber thread obtained by subjecting an open carbon fiber thread from a carbon fiber raw thread to twisting and a method for manufacturing the same, in particular, it relates to a superfine carbon fiber thread with further improved tensile strength obtained by a superfine thread made by forming a composite of open carbon fibers by covering and a method for manufacturing the same as we as by a superfine thread made by laminating various types of ultra-thin films onto open carbon fibers and then finishing them by a slitting machine and a method for manufacturing the same.

In view of the current situation, the inventors have performed the following two processes to manufacture a composite thread: (1) manufacturing a desired composite thread by opening open carbon fibers, slitting the opened fibers, twisting the slit fibers, and forming a composite of the fibers with a composite thread, and (2) performing the process of laminating a film (film of composite materials) while performing the process of opening open carbon fibers, and then slitting, twisting, and heating it for stress relief to manufacture a composite thread.

The first aspect of the instant invention relates to a superfine open carbon fiber thread characterized by being obtained by opening a carbon fiber resin tape formed from 12K or 24K raw threads, slitting the opened tape, twisting the slit tape, and forming a composite of the tape; wherein said forming a composite of the tape comprises S-winding and Z-winding covering; and said forming a composite of the tape comprises obtaining a composite thread material from one or more types of fine threads selected from the group consisting of copper wire, aluminum wire, brass wire, iron-chrome wire, Inconel (registered trademark) wire, tin wire, thermoplastic resin thread, thermosetting resin thread nylon, stainless steel wire, and inorganic material wire.

The second aspect of the instant invention relates to a superfine open carbon fiber thread characterized by being obtained by opening a carbon fiber resin tape formed from 12K or 24K raw threads, laminating and forming a composite of the tape, slitting the laminated tape, and twisting the superfine width laminated material obtained from said slitting; wherein said film comprises a membrane or nonwoven fabric, and is one or more materials selected from the group consisting of ePTFE, nylon 66, ABS, PET, PVA, polyester, silk, cotton, polyimide, and aramid resin.

The third aspect of the instant invention relates to a strand or woven yarn characterized in that open carbon fibers according to the first aspect are arranged as warp and weft threads, respectively, and the threads have a width of 1.5 to 12.5 mm after the slit, are twisted 10 time/m to 120 times/m, and have a diameter of 0.1 to 1.0 m/mφ.

The fourth aspect of the instant invention relates to a strand or woven yarn as described in the second aspect; wherein open carbon fibers according to the second aspect are arranged as warp and weft threads, respectively, and the threads have a width of 1.5 to 12.5 mm after the slit, are twisted 10 time/m to 120 times/m, and have a diameter of 0.1 to 1.0 m/mφ; and wherein a film comprising said membrane and nonwoven fabric has a thickness of 1 μm or less to 30 μm or less.

In addition, said strand or woven yarn are preferably used for a fishing net through a fishing net machine.

The fifth aspect of the instant invention relates to a method for manufacturing a superfine open carbon fiber thread, comprising:

-   -   a step of preparing carbon fibers as raw threads (carbon         fiber-preparing step),     -   a step of obtaining an open fiber tape by opening the raw         threads, using an opening machine (fiber-opening step),     -   a step of continuously split slitting the open fiber tape until         the minimal width reaches about 2 mm, subsequent to laminating         nylon 66 synthesized with 9% NMP onto the open fiber tape         (slitting step),     -   a step of continuously subjecting the open fiber tape with a         superfine width obtained from the slitting to twisting to         process it into a superfine thread (twisting step), and     -   a step of making a composite thread by S-winding and Z-winding         threads of various types of fine thread materials to said         superfine thread (composite thread-making step), wherein said         various types of fine thread materials include one or more types         selected from the group consisting of nylon, stainless steel         wire, PTFE, Kevlar (registered trademark) (aramid resin) and         Inconel (registered trademark) wire.

The sixth aspect of the instant invention relates to a method for manufacturing a superfine open carbon fiber thread, comprising:

-   -   a step of preparing carbon fibers as raw threads (carbon         fiber-preparing step),     -   a step of obtaining an open fiber tape by opening the raw         threads, using an opening machine (fiber-opening step),     -   a step of impregnating the open fiber tape with a sizing resin         from 0.5 to 5% while opening, wherein the sizing resin is         selected from the group consisting of potassium persulfate and         PVA (impregnating step),     -   a step of laminating and adhering one or more types of films         selected from the group consisting of ePTFE film, nylon 66, ABS,         PET, PVA, polyester, silk, cotton, polyimide, and aramid resin         onto the open fiber tape and forming a composite of the open         fiber tape (adhering and forming a composite step),     -   a step of continuously slitting the open fiber tape to 1.5 mm to         12.5 mm width, using a slitting machine to obtain a fine width         tape with a cut width (slitting step), and     -   a step of subjecting the thread to twisting, using a twisting         machine, for finishing treatment (twisting step).

The fiber-opening step is preferably a step of opening to flatten a 6 mm width bundle of 12K raw threads to a 24 to 25 mm width bundle, using an opening machine.

In addition, the twist is performed preferably 60 times/m.

In addition, the lamination is preferably single-sided lamination.

Preferably, the method further comprises a step of preventing the return of the twist for the finished thread by shaping the thread at 90° C. to 120° C. through a heater nozzle and removing stress.

A superfine open carbon fiber thread according to the first aspect of the instant invention is characterized by being obtained by opening a carbon fiber resin tape formed from 12K and 24K raw threads, slitting the opened tape, twisting the slit tape, and forming a composite of the tape, wherein said forming a composite of the tape comprises S-winding and Z-winding covering, and said forming a composite of the tape comprises obtaining composite thread materials from one or more types of fine threads selected from the group consisting of copper wire, aluminum wire, brass wire, iron-chrome wire, Inconel (registered trademark) wire, tin wire, thermoplastic resin yarn, thermosetting resin yarn nylon, stainless steel wire, inorganic material wire; and thus the tensile strength improves over conventional twisted threads, and the flexural strength and the repeated flexural strength increase by 10% or more, making the threads applicable to a variety of applications such as wire harness and flexible circuit boards.

A superfine open carbon fiber thread according to the second aspect of the instant invention is characterized by being obtained by opening, laminating and compositing a carbon fiber resin tape formed from 12K and 24K raw threads, and twisting the superfine width laminated material obtained from the slitting, wherein the superfine open carbon fiber thread comprises a laminated film, said film is formed from a membrane or nonwoven fabric, and is a material selected from the group consisting of ePTFE, nylon 66, ABS, PET, PVA, polyester, silk cotton, polyimide, and aramid resin; and thus, the flexural strength and the repeated flexural strength increase by 10% or more over conventional twisted threads.

Further, the superfine open carbon fiber thread according to the first and second aspects of the instant invention has tensile strength improvement of 10% or more over the base thread of a raw thread and can be used in a wide range of applications.

Furthermore, a strand according to the third and fourth aspects of the instant invention and can be made into a strand with arrangement of the warp and weft threads according to the intended use, which is particularly useful in applications requiring heat resistance and strength, such as sports products such as sneakers, pads for brake linings, core materials for a wire harness, EV motor windings, flexible substrates, and drone blades.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram of steps of manufacturing a carbon fiber composite thread according to one embodiment.

FIG. 2 is a photograph that shows an example of a carbon fiber composite thread according to Example 1.

FIG. 3 is a diagram of steps of manufacturing a carbon fiber composite thread laminate of FIG. 2 .

FIG. 4 is a photograph that shows an example of a carbon fiber composite thread laminate obtained by a manufacturing step of FIG. 3 .

FIG. 5 is a photograph that shows an example of a strand obtained in Example 3.

FIG. 6 is a photograph that shows an example of a strand obtained in the Example 3.

FIG. 7 is a photograph that shows an example of a net obtained in Example 4.

FIG. 8 is a cross-sectional illustration that shows an example of a carbon fiber composite thread configuration according to one embodiment of the instant invention.

FIG. 9 is an illustration that illustrates the structure of a carbon fiber composite thread of FIG. 8 , which is plainly woven in the longitudinal and transverse directions.

FIG. 10(a) is an illustration that illustrates a superfine carbon fiber thread according to a comparative example.

FIG. 10(b) is an enlarged external view of a superfine carbon fiber thread of FIG. 10(a).

FIG. 10(c) is a cross-sectional illustration of a superfine carbon fiber thread of FIG. 10(a).

FIG. 11(a) is an illustration of a carbon fiber composite thread according to an example 1.

FIG. 11(b) is an enlarged external view of a carbon fiber composite thread of FIG. 11(a).

FIG. 11(c) is a cross-sectional illustration of a carbon fiber compositing thread of FIG. 11(a).

FIG. 12(a) is an illustration of a composite carbon fiber thread according to a variation of an example 1.

FIG. 12(b) is a cross-sectional illustration of a carbon fiber composite thread of FIG. 12(a).

FIG. 13(a) is a plain view of an example of a carbon fiber composite thread according to Example 1 being applied to a plain woven product.

FIG. 13(b) is a cross-sectional illustration of a carbon fiber composite thread of FIG. 13(a).

FIG. 14(a) is a conceptual diagram of a method for manufacturing a flexible substrate of a carbon fiber composite thread according to Example 1.

FIG. 14(b) is an illustration of the obtained flexible substrate.

FIG. 14(c) is an illustration of an insulator of the flexible substrate of FIG. 14(b).

FIG. 15 is an illustration that shows an example of a parabolic antenna application of a carbon fiber composite thread from FIG. 13(a).

FIG. 16 is a cross-sectional illustration of a conventional wire harness.

FIG. 17 is a cross-sectional illustration that shows an example of a carbon fiber composite thread of FIG. 13(a) being applied to a wire harness.

DETAILED DESCRIPTION OF THE INVENTION

A superfine open carbon fiber thread (composite thread) according to embodiments of the instant invention is manufactured by the two methods described below.

<(1) A method 1 for manufacturing a superfine thread (composite thread)

In one embodiment, a superfine thread (composite thread) is made from a carbon fiber and raw thread (strand) via the following steps (see FIG. 1 ).

-   -   (a) Fiber-opening step. In this step, for example, 6 mm bundle         width of 12K raw thread is flattened into 24 to 25 mm width.     -   (b) Slitting step. In this step, the flattened raw thread is         continuously split slit to a minimum width of about 2 mm in         24-25 mm widths to obtain a superfine width open-fiber tape.     -   (c) Twisting step. In this step, the superfine width open fiber         tape obtained in the above slitting step, is continuously         twisted and processed into a superfine thread. In other words, a         “superfine carbon fiber thread” is obtained.     -   (d) Composite thread-making step (performing a covering step),         S-winding and Z-winding are performed on a superfine thread         (superfine carbon fiber thread) obtained by a continuous         twisting in the above step (c) to cover with various fine         material threads. In this step, any desired composite thread of         material is made with fine thread material threads composed of         one or more selected from copper wire, aluminum wire, brass         wire, iron-chrome wire, Inconel (registered trademark) wire, tin         wire, thermoplastic resin yarn, thermosetting resin yarn nylon,         stainless steel wire, inorganic material wire (glass, ceramic)         and the like.

Referring to FIG. 8 , a composite thread material according to another embodiment is composed of:

-   -   a core material (CF) as a first layer with a superfine carbon         fiber thread obtained in the above step (c);     -   a cover layer (N) as a second layer that covers CF by S-winding         and Z-winding of a nylon 6, nylon 66, or nylon 9 around the         above first layer (core material (CF)); and a third layer (cover         layer (Cu)) obtained by further S-winding and Z-winding of a         copper wire on the above second layer (cover layer (N)).

In more detail, the superfine carbon fiber thread obtained in the above step (b) is a striatum that is from 0.75K to 1.5K and has a diameter of 0.15 to 0.25 mmφ (See FIG. 10(a), FIG. 10(c) and is twisted (See FIG. 10(b)).

Then, referring to FIGS. 12(a) and 12(b), according to the above step (c), a cover layer (N) is obtained by covering the superfine carbon fiber thread with, for example, a nylon thread (nylon 6) (see FIGS. 11(a), 11(b) and 11(c)).

Next, according to the above step (c), a cover layer (Cu) is formed by S-winding and Z-winding with a superfine copper wire on the cover layer (N) of FIG. 11(a) to obtain a composite thread (1). The diameter of the composite thread (1) is preferably from 0.2 to 05 mmφ.

As another embodiment, FIG. 9 shows a plain woven structure in which this composite thread material (1) is arranged vertically and horizontally, and this plain woven structure can be suitably employed as, for example, a flexible substrate.

FIGS. 14(a), 14(b), and 14(c) illustrate the concept of how to obtain a flexible substrate from a plain woven structure shown in FIG. 9 .

First, after placing an insulating plate (In) made of a thermoplastic resin (e.g., nylon 6, nylon 9, polypropylene, etc.) on one side of a plain woven structure (PW), a thermal rolling process is applied by a rolling roll at a temperature of 90° C. to 180° C. When it is rolled to a thickness (t) of 0.1 to 0.5 mm (see FIG. 14(a)), a flexible integrated product is obtained (see FIG. 14(b)). When one side (insulating side In) of this integrated product is processed with a baked coating such as Quatlon (registered trademark), excellent dielectric strength and dielectric loss tangent (0.02) can be obtained (see FIG. 14(c)). The dielectric loss tangent refers to the loss of electrical energy inside the insulator (a criterion for evaluating performance as an insulator).

On the other hand, a copper surface (Cu) is formed uniformly on the other side of this integrated product.

Therefore, this integrated product with semiconductor parts added thereto can suitably achieve its purpose as a flexible substrate.

As yet another embodiment, a composite thread material of the instant invention can be applied to a parabolic antenna (PA) as shown in FIG. 15 , by the same manufacturing method as the above flexible substrate when it forms a plain woven structure as shown in FIG. 9 .

As yet another embodiment, a composite thread material of the instant invention can be suitably applied to a thin wire for a wire harness.

A currently commercially available conventional thin wire for a wire harness has a cross-sectional configuration as shown in FIG. 16 . That is, it is composed of a center section and a copper wire arranged around the center section. In addition, the center section is composed of chemical fibers such as Kevlar (registered trademark) (aramid resin), which has the disadvantage of being vulnerable to heat and ultraviolet rays.

In contrast, when a composite thread material of the instant invention is applied to a thin wire for a wire harness, it has a cross-sectional configuration as shown in FIG. 17 . That is, a superfine carbon fiber thread of the instant invention is arranged in the center section, and a cover layer (N) consisting of a nylon resin thread is arranged around the superfine carbon fiber thread, and a superfine copper wire (wire diameter 0.05 mmφ to 0.20 mmφ) is arranged in the outer layer therearound. This can provide the advantage of resistance to the heat and ultraviolet rays.

Moreover, a composite thread material of the instant invention is also suitably applicable for wires such as aerial transmission cables for various types of wires, as well as various types of ribbons and flat cables.

<(2) A method 2 for manufacturing a superfine thread (composite thread)>

A superfine thread is manufactured from a carbon fiber and raw thread (strand) via the following steps.

(Step a) Opening fiber step. For example, a step of flattening a 6 mm bundle width of a 12K raw threads into a 24-25 mm width to make a tape form.

(Step b) Adhering and forming a composite step. This step is a step to impregnate an open-carbon fiber resin that has been made into a tape form in the previous step with PVA, epoxy resin, and 1 to 3% aqueous solution, and then adhere and form a composite of this, a lengthy manufactured product in any width, as well as various kinds of thin films (3 μm to 30 μm thick) by a heating roll.

For the sizing agent used in this step, PVA, alumina sol, benzoyl with OH groups, etc., are also suitably adopted.

For the various thin film materials used in this step for the purpose of forming a composite, nylon 6, 12, 66, nylon 9, PP, urethane, e-PTFE, membrane, etc. can be suitably adopted.

(Step c) Slitting step. This step is a step to continuously slit the tape of 24-25 mm width (a width of an open fiber tape obtained in the above step) to any desired width (1.5 to 5 mm width) by a slitting machine.

(Step d) Twisting step. This step is a step to obtain a composite thread by finishing a superfine width laminated material obtained in the above step c into a twisting thread.

In this step, a tensile strength of a composite thread was surprisingly increased by 10% or more, when a twisting machine provided an average of 90 twists per unit meter with a resin being outside.

The tendency for tensile strength of the superfine open carbon fiber thread and the composite thread (including each type of covering materials) to be lower than that of a raw thread (strand) has been found.

The inventors of the instant invention have also attempted to experiment with a superfine composite thread, taking into consideration the environment and productivity of the production site.

That method includes (i) a composite covering method, (ii) a resin impregnation method, and (iii) a method of finishing a superfine thread, by laminating various types of ultra-thin films onto an open carbon fiber, slitting the fiber to a narrow width (1.5-12.5 mm width, preferably 2.0-5.0 mm width) with a slitting machine, and then adding a twist of 10 times/m to 120 times/m, preferably 60 times/m-90 times/m, with a twisting machine. Superfine composite threads were made to be suitable for various application products.

From these open carbon fibers, the following procedures were established to complete various types of superfine threads and commercialize them into applied products.

-   -   1. Preparing a carbon fiber (raw thread and strand)     -   2. The raw thread is opened to a width of 4 to 5 times of the         raw thread, with a fiber opening machine. It is impregnated with         0.5 to 5% of various sizing resins, at the same time as opening.         A film is laminated and adhered onto the open fiber tape at the         same time. In this case, the tape can be made of any available         cloth, membrane, or non-woven (film like) material such as         ePTFE, nylon 66, nylon 9, ABS, PET, PVA, polyester, silk,         cotton, polyimide, and polyamide resin. The thickness of the         film (including FEP and PFA) is not limited as long as it is         superfine and tensile resistant. It is preferably 1 μm or less         to 30 μm or less, 1 μm to 30 μm, particularly 5 to 10 μm. In         this case, the laminate can be preferably a single-sided or         double-sided, particularly single-sided. It is also important         that the tape is colored if necessary.     -   3. A slitting machine continuously slits the tape from 1.5 mm to         12.5 mm in width to obtain a fine width tape with a cut width.     -   4. A twisting machine twists the tape 10 times/m to 120 times/m         into a twisted thread for finishing treatment. In this case,         depending on the application, either a resin side can be         surfaced or a carbon fiber side can be surfaced. In order to         prevent the return of the twist for a thread comprising these         resins when finished, it is recommended to shape the thread         (stress removal) at 90° C. to 120° C. through a heater nozzle.     -   5. As a finished thread according to the instant invention, a         thread of φ 0.1 to 1.0 m/m can be used for multipurpose         applications. The thread of the instant invention can be used         for any products to which thread-knitting may be applied, such         as woven fabrics, knitted fabrics, sewing threads, woven         fabrics, tents, canvas, textiles, nets, fishing nets, sneakers,         sporting goods, or brake pad materials.

To sum up, methods for making superfine threads composed of open carbon fiber according to the embodiments of the instant invention include the following two methods:

(Method 1) An open carbon fiber is opened, the opened fiber is slit, the slit fiber is twisted and a composite is formed with a composite thread to complete a desired composite thread.

(Method 2) While an open carbon fiber is opened, the fiber is laminated with a film (film of composite materials), slit, twisted and heated for stress relief to complete a desired composite thread. As a result of experiments, the tensile strength of the above thread was found to be improved by 10% or more when compared with a base thread of a raw thread, which is suitable for a variety of applications as described above.

Regarding the superfine open carbon fiber thread of the instant invention, in the case when the superfine thread is obtained by the above-mentioned “Method 1”, the way of knitting may be limited if the efficiency (productivity) is not relatively high or the tension of the finished thread becomes relaxed in the covering step.

On the other hand, in the case when the superfine thread is obtained by the above-mentioned “Method 2”, a more complete superfine open carbon fiber can be made because, after completion of a composite thread, passing the composite thread through a heat treatment dice ensures a better fitting into a superfine carbon fiber thread. When these properties are considered, the superfine threads of the above-mentioned “Method 1” and “Method 2” can be used for different applications.

EXAMPLE

The instant invention will be described in detail on the basis of following examples. However, it should be understood that the instant invention is not intended to be interpreted as limited to only the examples.

1K, 3K, 6K, 12K, and 24K raw threads of the above-mentioned acrylic-based carbon fiber described above are known to exhibit constant strength values, respectively.

The inventors measured and validated the strength values of the raw threads of these acrylic-based carbon fiber using a tensile testing machine, and confirmed that the measured strength values show the almost same values with the published values by other companies (Toray Industries, Inc. and Teijin Limited).

Next, the inventors conducted an experiment to measure the strength values of 3K, 6K, 12K, and 24K raw carbon fiber threads in which the number of twisting applied to each of these carbon fiber base threads are from 10 to 120/meter. The tensile strength values (in kN) are provided in the following “Table 1”.

A raw thread was used as supplied by a manufacturer (3K, 6K, 12K, and 24K) (see the columns “Raw Thread” in Tables 1, 2, and 3).

As comparable example, 3K, 6K, 12K, and 24K raw threads, to which 120 twists/m (times/m) are applied after fiber-opening, were employed.

Example 1 Manufacturing Example 1 of a Superfine Thread (Applied to Fishing Nets, Etc.)

12K raw threads made by Formosa Plastic Group were used as carbon raw fiber threads, and a 6 mm width bundle of 12K raw threads were flattened into a tape shape with 24-25 mm width ((a) fiber-opening step). Then, the 24-25 mm bundle width was continuously slit by using specialized equipment so that a minimum width becomes about 2 mm ((b) slitting step).

After synthesizing NMP 9% with a modified nylon of soluble nylon 6 from Namariichi Corporation, the open-fiber tape was impregnated with 3-6% sizing resin, and was slit. This was effective in preventing a composite thread in covering from shifting and fluffing.

Subsequently, the superfine width open fiber tape obtained by slitting was continuously twisted (60 times/m) to process it into a superfine thread ((c) twisting step).

Finally, the superfine thread, which was a carbon fiber continuously twisted into a superfine thread, was winded in S-winding and Z-winding to obtain various types of fine thread material, and a composite of the superfine thread is formed with (1) nylon 9, (2) PTFE, or (3) aramid fibers to obtain desired composite thread materials ((d) composite thread-making step).

The twisted yarn thus obtained is shown in FIG. 2 .

Manufacturing Example 2 of a Superfine Thread (Applicable to Fishing Nets, Etc.)

See FIG. 3 .

12K raw threads made by Formosa Plastic Group were used as carbon fiber threads, and 6 mm bundle width of 12K raw threads was flattened into a tape shape with 24-25 mm width to obtain an open fiber tape ((a) fiber-opening step). This open fiber tape was laminated with 20 μm of ePTFE membrane (made by Donaldson, U.S.A.) using a potassium persulfate and PVA adhesion ((b) adhering and forming a composite step), and the resulting product was slit into a width of 2.5 mm ((c) slitting step). The film (membrane) has a thickness from 5 μm to 10 μm. The superfine width laminated material obtained by slitting was twisted at 60 times/m ((d) twisting step) to finish a twisted thread. The example of the resulting twisted thread is shown in FIG. 4 .

TABLE 1 Composite Data A B C D Classification materials Standard value 3K 6K 12K 24K Remarks Raw thread Base width (mm) 3 4 6 7.3 Tensile force (kN) 0.21 0.36 0.71 0.92 Comparative Tensile strength of 0.21 0.39 0.76 0.94 example twisted thread (kN) Example 1 (1) Nylon 9 Tensile strength of 0.29 0.42 0.83 Twisting 60 thread twisted thread (kN) times/m, 0.3 mm thickness (2) PTFE Tensile strength of 0.29 0.49 0.92 Twisting 60 thread twisted thread (kN) times/m, 0.15 mm thickness (3) Aramid Tensile strength of 0.36 0.56 1.06 Twisting 90 thread twisted thread (kN) times/mm, 0.15 mm thickness (4) PTFE Tensile strength of 0.29 0.49 0.92 Twisting 90 film twisted thread (kN) times/mm, 25 microns

[Example 2] Manufacturing Example of a Superfine Thread (Applicable to Flexible Circuit Boards, Etc.)

12K raw threads made by Formosa Plastic Group were used as carbon raw fiber threads, and a 6 mm width bundle of 12K raw threads were flattened into a tape shape with 24-25 mm width ((a) fiber-opening step). Then, the 24-25 mm bundle width was continuously slit by using specialized equipment so that a minimum width becomes about 2 mm ((b) slitting step).

After synthesizing NMP 9% with a modified nylon of soluble nylon 6 from Namariichi Corporation, the open-fiber tape was impregnated with 3-6% sizing resin, and was slit. This was effective in preventing a composite thread in covering from shifting and fluffing.

Subsequently, the superfine width open fiber tape obtained by slitting was continuously twisted (60 times/m) to process it into a superfine thread ((c) twisting step).

Finally, the superfine thread, which was a carbon fiber continuously twisted into a superfine thread, is winded in S-winding and Z-winding to obtain various types of fine thread material threads, and a composite of the superfine thread is formed with (1) copper wire or (2) aluminum wire to obtain desired composite thread materials ((d) composite thread-making step).

TABLE 2 Composite Data A B C D Application Classification materials Standard value 3K 6K 12K 24K examples Raw thread Base width (mm) 3 4 6 7.3 Tensile force (kN) 0.21 0.36 0.71 0.92 Comparative Tensile strength of 0.21 0.43 0.84 1.32 example twisted thread (kN) Example 2 (1) Copper Tensile strength of 0.32 0.54 0.96 Twisting 90 wire twisted thread (kN) times/mm, 0.12 mm thickness (2) Tensile strength of 0.38 0.62 1.00 Twisting 90 Aluminum twisted thread (kN) times/mm, 0.15 mm wire thickness

[Example 3] Manufacturing Example 3 of a Superfine Thread (Applied to a Wire Harness, Etc.)

12K raw threads made by Formosa Plastic Group were used as carbon raw fiber threads, and a 6 mm width bundle of 12K raw threads were flattened into a tape shape with 24-25 mm width ((a) fiber-opening step). Then, the 24-25 mm bundle width was continuously slit by using specialized equipment so that a minimum width becomes about 2 mm ((b) slitting step).

After synthesizing NMP 9% with a modified nylon of soluble nylon 6 from Namariichi Corporation, the open-fiber tape was impregnated with 3-6% sizing resin, and was slit. This was effective in preventing a composite thread in covering from shifting and fluffing.

Subsequently, the superfine width open fiber tape obtained by slitting was continuously twisted (60 times/m) to process it into a superfine thread ((c) twisting step).

Finally, the superfine thread, which was a carbon fiber continuously twisted into a superfine thread, is winded in S-winding and Z-winding to obtain various types of fine thread material threads, and a composite of the superfine thread is formed with (1) copper wire or (2) aluminum wire to obtain desired composite thread materials ((d) composite thread-making step).

TABLE 3 Composite Data A B C D Application Classification Materials Standard value 3K 6K 12K 24K examples Classification Base width (mm) 3 4 6 7.3 Tensile force (kN) 0.21 0.36 0.71 0.92 Comparative Tensile strength of 0.21 0.22 0.32 0.29 example twisted thread (kN) Example 3 (1) Copper Tensile strength of 0.32 0.54 0.96 Twisting 90 wire twisted thread (kN) times/m (2) Tensile strength of 0.38 0.62 1.00 Twisting 90 Aluminum twisted thread (kN) times/m wire

Evaluation of Examples 1-3 (A) A Superfine Thread of Example 1 (Applied to Fishing Nets, Etc.)

The superfine threads of Example 1, which have (1) nylon 9 thread, (2) PTFE thread, (3) aramid thread, or (4) PTFE film as a material, were found to have superior tensile strength of twisted thread when compared with the comparative example, as shown in Table 1.

Therefore, a nylon composite thread was woven with the composite thread obtained in Example 1 using a fishing netting machine, in order to obtain a fishing net. The fishing net thus obtained is shown in FIG. 7 . This fishing net was resistant to tearing and cutting, and thus, can exert high performance when actually used in the fishing industry.

(B) A SUPERFINE THREAD OF EXAMPLE 2 (APPLIED TO FLEXIBLE CIRCUIT BOARDS, ETC.)

The superfine threads of Example 2, which have (1) copper wire or (2) aluminum wire as a material, were found to have superior tensile strength of twisted thread when compared with the comparative example, as shown in Table 2.

Therefore, it is presumed that the superfine threads obtained in Example 2 can be applied to flexible circuit boards.

(C) A Superfine Thread of Example 3 (Applied to Wire Harnesses, Etc.)

For the superfine threads of Example 3, which have (1) copper wire or (2) aluminum wire as a material, were found to have superior tensile strength of twisted thread when compared with the comparative example, as shown in Table 3.

Therefore, it is presumed that the superfine threads obtained in Example 3 can be applied to wire harness.

In general, the superfine thread of the instant invention can be used in, for example, manufacturing thread with almost any type of knitting machine, plain weave means, twill weave means, spoon weave means, circular weave means, knit-knitting means, circular knitting means, fishing net-knitting machine, braiding machine, braided cord machine, sewing machine, broad weave machine, sock-knitting means, glove-knitting means, and sneaker-knitting machine. Therefore, the instant invention can be widely used for tent cloth, canvas cloth, fire curtain, flexible cloth, brake lining pad, high-temperature bag filter, as well as, in accordance with composing with resin (thermoplastic or thermosetting), home appliance, semiconductor, smartphone TV, EV motor, drone wing, round bar, plate material, 2×4 stay for housing, and small parts in automobiles, aircraft, ships, etc., and can be freely selected for strength design distribution in each part. For example, the use of each woven thread can be selected according to the arrangement of warp and weft threads. 

1. A superfine open carbon fiber thread obtained by opening a carbon fiber resin tape formed from 12K or 24K raw threads, slitting the opened tape, twisting the slit tape, and forming a composite of the tape, wherein said forming a composite of the tape comprises an S- and Z-winding covering, and wherein said forming a composite of the tape comprises obtaining composite thread materials from one or more types of fine threads selected from a group consisting of copper wire, aluminum wire, brass wire, iron chrome wire, Inconel (registered trademark) wire, tin wire, thermoplastic resin thread, thermosetting resin thread nylon, stainless steel wire, copper wire, and inorganic material wire.
 2. A superfine open carbon fiber thread obtained by opening a carbon fiber resin tape formed from 12K or 24K raw threads, laminating the opened tape, slitting the laminated tape, and twisting the superfine width laminated material obtained from said slitting, wherein the superfine open carbon fiber thread comprises a laminated film, and wherein said film comprises a membrane or non-woven fabric and is a material selected from a group consisting of ePTFE, nylon 66, ABS, PET, PVA, polyester, silk, cotton, polyimide, and aramid resin.
 3. A strand or woven yarn of superfine open carbon fibers according to claim 1 arranged as warp and weft threads, respectively, wherein the superfine open carbon fibers have a width of 1.5 to 12.5 mm after said slitting, are twisted 10 times/m to 120 times/m, and have a diameter of 0.1 to 1.0 m/mφ.
 4. A strand or woven yarn of superfine open carbon fibers according to claim 1 arranged as warp and weft threads, respectively, wherein the superfine open carbon fibers have a width of 1.5 to 12.5 mm after said slitting, are twisted 10 times/m to 120 times/m, and have a diameter of 0.1 to 1.0 m/mφ, and wherein said film including a membrane or non-woven fabric has a thickness of 1 μm or less to 30 μm or less.
 5. The strand or woven yarn according to claim 3 or 4, wherein the strand or woven yarn are used for a fishing net through a fishing net machine.
 6. A method for manufacturing a superfine open carbon fiber thread, comprising steps of: preparing carbon fibers as raw threads (carbon fiber-preparing step); obtaining an open fiber tape by opening the raw threads, using a fiber opening machine (fiber-opening step), continuously split slitting the open fiber tape until a minimal width reaches about 2 mm, subsequent to laminating nylon 66 synthesized with 9% NMP onto the open fiber tape (slitting step), continuously subjecting the open fiber tape with a superfine width obtained from the slitting to twisting to process it into a superfine thread (twisting step), and making a composite thread by an S- and Z-winding threads of various types of fine thread materials threads to said superfine thread (composite thread-making step), wherein said various types of fine thread materials include one or more types selected from a group consisting of copper wire, aluminum wire, brass wire, iron-chrome wire, Inconel (registered trademark) wire, tin wire, thermoplastic resin thread, thermosetting resin thread nylon, stainless steel wire, copper wire and inorganic material wire.
 7. A method for manufacturing a superfine open carbon fiber thread, comprising steps of: preparing carbon fibers as raw threads (carbon fiber-preparing step), obtaining an open fiber tape by opening the raw threads, using a fiber opening machine (fiber-opening step), impregnating the open fiber tape with a sizing resin from 0.5 to 5% while opening, wherein the sizing resin is selected from a group consisting of potassium persulfate and PVA (impregnating step), laminating and adhering an ePTFE film onto said open fiber tape (adhering step), continuously slitting the open fiber tape to 1.5 mm to 12.5 mm width, using a slitting machine (slitting step), and subjecting the thread to twist, using a twisting machine, for finishing treatment (twisting step).
 8. The method for manufacturing according to claim 6 or 7, wherein said opening is a step of opening a 6 mm width bundle of 12K raw threads to a 24 to 25 mm width bundle, using an opening machine.
 9. The method for manufacturing according to claim 7, wherein said twisting is performed 60 times/m.
 10. The method for manufacturing according to claim 7, wherein said lamination is single-sided lamination.
 11. The method for manufacturing according to claim 7, further comprising a step of preventing return of the twist for the finished thread by shaping the thread at 90° C. to 120° C. through a heater nozzle and removing stress. 